Are Cows Showing You Their Rumen pH?

For the modern dairy cow, it’s commonplace to spend up to 11.9 hours a day with a lowered rumen pH, which can mean nearly half a day of impaired digestion.

The time spent below a pH of 5.8 is known as Sub Acute Rumen Acidosis (SARA). Costs from SARA are estimated at $1.12 per cow daily, making it recognized as the most important nutritional issue of dairy cattle on a herd basis.

“Not surprisingly, SARA can result in adverse health events that can lower milk yield and reproductive performance,” says Anthony Hall, MSc MSB, PAS, Technical Services, Ruminant, with Lallemand Animal Nutrition. “The costs from SARA range from less efficient use of feedstuffs to serious and ongoing health challenges that can lead to increased culling rates. Yet, if we listen to what the cows are telling us, we can stop the effects of SARA before it starts.”

SARA episodes can be categorized into two main types: sudden-onset and recurrent.

Sudden-onset SARA episodes are short durations of time generally associated with the consumption of large quantities of rapidly fermentable carbohydrates. This shifts the microflora in the rumen and creates an environment where lactate-producing species, such as S. bovis, can proliferate. Recurrent SARA can have many long-standing effects in the rumen, organ and skeletal systems, hoof-related disorders, clinical illness and even death.

“Recurrent SARA can cause rumen wall erosion that can lead to bacteria entering the blood stream,” Hall notes. “From the blood stream, bacteria travel and cause liver abscesses and damage to the heart, lungs or joints.”

Most dairy cattle don’t exhibit any overt signs of SARA. Most commonly, cattle will eat more sporadically or even reduce their feed consumption. However, the subtle individual behavior can go unnoticed in commercial herds. Other signs of SARA include:

Reduced dry matter intake

Reduced cud-chewing

Mild diarrhea or inconsistent fecal texture

Foamy feces containing gas bubbles

Reduction of milk component yield and component yield inversion

Increased incidence of gram-negative mastitis

Undesirable cleanliness and hygiene scores

Proper feed bunk management, ration formulation, mixing and delivery can help protect the entire herd from experiencing the consequences of SARA. When SARA occurs, however, the rumen function isn’t optimized to make the best use of any ration. Even in-feed buffers like sodium bicarbonate can’t eliminate the risk of SARA.

Probiotic feed additives that improve rumen function and increase fiber digestion can help maximize rumen function in all life stages of dairy cattle.

“While all dairy cattle are at risk for SARA, the most commonly affected lactating groups are fresh cows and high-yielding cows,” Hall says. “It’s particularly important to monitor these groups for signs of SARA.”